Drugs may be delivered to patients by a variety of methods including oral, intravenous, intramuscular, inhalation, topical or subcutaneous delivery. The drug may be delivered directly or locally to the treatment site (e.g., intrathecally, intraspinally, intraarticularly, etc.). The method of delivery chosen depends upon, among other things, the condition being treated, and the desired therapeutic concentration of the drug to be achieved in the patient and the duration of drug concentration that must be maintained.
Drug depots have been developed, which allow a drug to be introduced or administered to sites beneath the skin of a patient. The drug depot releases the drug over a period of time. Drug depots allow the drug to be released from the depot in a relatively uniform dose over weeks, months or even years. Administering drugs using drug depots is becoming especially important and popular in modulating the immune, inflammation and/or pain responses in treatment of chronic conditions including rheumatoid arthritis, osteoarthritis, sciatica, carpal tunnel syndrome, lower back pain, lower extremity pain, upper extremity pain, cancer, tissue pain and pain associated with injury or repair of cervical, thoracic, and/or lumbar vertebrae or intervertebral discs, rotator cuff, articular joint, TMJ, tendons, ligaments, muscles, and the like.
Drug depots are typically inserted into a treatment site beneath the skin of a patient by use of a trocar device, which is a two-piece device that includes a cannula and an obdurator. The trocar device requires an incision to be made through the skin using a separate instrument (e.g., scalpel) so that the drug depot can be moved through the incision to an implant site within the patient's anatomy. The cannula and obdurator may be inserted together through the incision. Next, the obdurator is withdrawn, leaving the cannula in place as a guide for inserting the drug depot. The drug depot is inserted through the cannula, and the obdurator is used to push the implant to the end of the cannula. The cannula and obdurator are then withdrawn completely, leaving the drug depot at the implant site.
Typically, trocar devices are used to implant drug depots subcutaneously over a large area (e.g., 2-2.5 inches), with a typical drug depot in the order of 1½ inches long. Thus, the trocar device is not suitable for many small or hard to reach treatment sites because it lacks precision and may cause additional trauma to the tissue surrounding the site of implant.
Other drug delivery devices have been developed that attempt to simplify implanting drug depots. These devices have a handle for one-handed implantation of a drug depot, a needle containing the drug depot to be implanted and a rod positioned within the needle for pushing the drug depot out of the needle. Once the needle containing the drug depot has been inserted at the site of implantation, a spring loaded trigger on the handle is activated, which causes the needle to be automatically withdrawn by a spring, thus leaving the drug depot at the site of implantation. Unfortunately, it is not possible to control the motion of the needle in these devices because the needle will automatically retract upon activation of the trigger. Furthermore, the complex spring loaded propelling system and trigger of these devices increase the likelihood that the device will jam and fail to eject the drug depot when required.
Conventional needle and syringe devices have also been used to implant a drug depot to sites within a patient, such as, for example, epidural space. These devices typically utilize a syringe that is preloaded with the drug depot. A needle of the syringe is inserted through the patient's skin, supraspinous ligament, intraspinous ligament, ligamentum flavum and into the epidural space. The drug depot is delivered through the needle to the epidural space by moving a plunger of the syringe relative to the needle. However, such devices do not allow for controlled and precision implantation of a drug depot. The ability to implant a drug depot in a controlled and precise manner is further reduced when such devices are used to implant multiple drug depots.
In devices used for drug depot implantation, drug depots are secured in a drug cartridge of the devices by use of a bulking agent. The bulking agent may be added to the drug depot to ensure the drug depot is secure within the drug cartridge, such that the drug depot is released when a plunger is engaged to dislodge the drug depot from the drug cartridge. The bulking agent may be added to the drug cartridge before the drug depot is added to the drug cartridge. The drug depot may also be added to the drug cartridge before the bulking agent is positioned within the drug cartridge, and the bulking agent is added to the drug cartridge after the drug depot has been positioned therein. Use of a bulking agent to retain the drug depot in a drug cartridge requires additional steps and is time consuming.
Treatment of patients with drug depots involves injecting one or a plurality of drug depots into the patient. In order to avoid injecting an incorrect number of drug depots, a drug delivery device should allow for visual verification of a number of drug depots loaded in the drug delivery device. Furthermore, since varying numbers of drug depots are used, it is desirable that a drug delivery device accommodate varying numbers of the drug depots. It is further desirable that a drug delivery device be tailored to specific numbers of drug depots. Still further, reliability of such drug delivery devices is important and such devices should therefore provide for jam free operation.
New drug delivery devices are needed, which can easily allow accurate and precise implantation of at least one drug depot with minimal physical and psychological trauma to a patient. When implanting a plurality of drug depots, a drug delivery device is needed that accurately and precisely allows placement of the drug depots in a manner such that one of the drug depot does not substantially interfere with the other drug depots.